Calcium Hormones: CLINICAL SIGNIFICANCE Flashcards
Most common cause of hypercalcemia combined effects of PTH function
Primary Hyperparathyroidism
CAUSED BY: parathyroid adenoma, hyperplasia, carcinoma, hereditary conditions
Primary hyperparathyroidism
Unique bone manifestation of PHPT
Bone pain and loss of bone mass
Calcified structures are replaced with fibrous tissue
Bone cyst formation
Osteitis Fibrosa Cystica
Hypercalcemia of Malignancy
Underlying cause is generally excessive bone resorption:
With bony metastases (common in hematologic malignancies)
• Direct tumor lysis
• Osteoclast-activating factor by tumor cells
• Lymphokines with osteoclast-potentiating activity (TNF, IL-1)
Hypercalcemia of Malignancy
Underlying cause is generally excessive bone resorption:
Without bony metastases
• Humoral hypercalcemia of malignancy
• Over-expression of PTH-related protein (PTHrP) in squamous cell and renal tumors
Other Causes of Hypercalcemia
VITAMIN D INTOXICATION (HYPERVITAMINOSIS D):
LITHIUM THERAPY:
HYPERCALCEMIA IN GRANULOMATOUS DISORDERS:
MILK-ALKALI SYNDROME:
VITAMIN D INTOXICATION (HYPERVITAMINOSIS D):______ times the normal requirement (> 40,000-100,000 U/d)
LITHIUM THERAPY:____ of patients
40-100
10%
unregulated generation of the active form of vitamin D by macrophages in granulomatous tissues (sarcoidosis, tuberculosis
HYPERCALCEMIA IN GRANULOMATOUS DISORDERS
increased intake of milk and
absorbable alkali to control gastric acid levels (antacids/calcium carbonate) in patients with peptic ulcers (much less frequent now)
MILK-ALKALI SYNDROME:
The calcium-sensing receptor on the
parathyroid cell is mutated
abnormal sensing of the blood calcium by the parathyroid gland and renal tubule
inappropriate secretion of PTH
excessive reabsorption of calcium in the distal renal tubules
Familial Hypocalciuric Hypercalcemia
Hallmark: low urinary calcium excretion
Familial Hypocalciuric Hypercalcemia
HYPOCALCEMIA
CAUSES:
•hypoparathyroidism
•deficiency of vitamin D
Hypoparathyroidism (3 types)
PTH-deficient hypoparathyroidism
PTH-ineffective hypoparathyroidism
PTH-resistant hypoparathyroidism
diminished or absent PTH production
PTH-deficient hypoparathyroidism
PTH-deficient hypoparathyroidism (2)
Acquired
Inherited
PTH-deficient hypoparathyroidism
acquired:
neck surgeries/thyroidectomy
PTH-deficient hypoparathyroidism
diminished or absent PTH production
Inherited: (2)
• Defective thymus and parathyroid gland (DiGeorge syndrome)
• hereditary autoimmune syndrome:
• Synthesis of biologically inactive
PTH
PTH-ineffective hypoparathyroidism
genetic disorder where the body fails to respond to PTH due to defect in
PTH receptor-adenylate cyclase complex
This causes low blood calcium levels and high blood phosphate levels.
Albright’s hereditary osteodystrophy
PTH-RESISTANT HYPOPARATHYROIDISM
Pseudohypoparathyroidism
Albright’s hereditary osteodystrophy
PTH-RESISTANT HYPOPARATHYROIDISM
Hypovitaminosis D
CAUSES:
• inadequate production of vitamin D
• insufficient dietary supplementation
• inability of Sl to absorb vitamin D
• vitamin D resistance
Hypovitaminosis D
EFFECTS:
• disturbances in mineral metabolism (rickets/osteomalacia)
Disorders of calcification
Osteomalacia
Rickets
• failure to mineralize newly formed organic matrix in bones
• bones become softer
OSTEOMALACIA (adults)
• osteomalacia before cessation of growth
• skeletal deformities (bowed legs, rachitic rosary)
RICKETS (children)
Rickets vs Osteomalacia
Rickets affects children, causing soft bones and bone deformities.
Osteomalacia affects adults, causing weak bones and increased fracture risk.
Both are due to vitamin D deficiency or impaired calcium absorption.
METABOLIC BONE DISEASES
Osteoporosis
• reduction in the strength of bone that leads to an increased risk of fractures.
• Loss of bone tissue is associated with deterioration in skeletal microarchitecture.
Osteoporosis
Measure or tests for osteoporosis
• Dual Energy X-ray Absorptiometry (DXA)
• Bone Mineral Densitometry:
• CT or MRI
• measures grams of calcium per square centimeter of cross sectional area of bone (g/cm2)
Bone Mineral Densitometry
HYPOCALCEMIA
Low calcium levels lead to increased nerve excitability
Hypoparathyroidism
2 signs of hypoparathyroidism or hypocalcemia
Chvostek sign
Trousseau sign
How to test:
1) Place blood pressure cuff around the arm
2) Inflate the cuff for 1-4 mins
3) If hands & fingers go into spasm in palmar flexion = positive
TROUSSEAU’S SIGN
How to test:
1) Tap the face just below and in front of the ear
2) If facial twitching occurs of one side of the mouth, nose & cheek = positive
CHOSTEK’S SIGN
